+100 on not starting out too fast. While a neck injury currently prevents me from riding like I would like, a couple years ago I was pretty much riding a metric century most weekends (until overuse injuries stopped that - but THAT is another story) I also like using a hydration pack on the bike, it is less complicated and insures that I will actually drink. Nothing wrong with stopping for a bite when you need to do so if you aren't comfortable eating while riding - I can do that if I have something in small enough pieces in my top tube bag, but I don't often do that. Having your Camelbak, depending on the size, will provide a bit extra room for storing things.

Have fun, pace yourself, and enjoy the event! Also agreed that you shouldn't take food/drink that you aren't accustomed to so think about having a little something with you in case they have different snacks/drink at the stops that you aren't accustomed to. Your first long ride isn't the time to experiment.